Fiberboard composition



APlll 18, 1944- F. RosENTHAl.

u FIBERBOARD COMPOSITION Filed April 19, 1941 v @MMM .MEN-D Mulan: .SDI Dumm Zul-.Cum

Patented Apr. 1.8,` 1944 2,346.94: l rmannoann comosmox Frits Rosenthal, Knoxville, Tenn., assigner to The University of Tennessee Research Corporation. Knoxville, Tenn., a corporation of Tennessee Application api-u 19, 1941, sensi No. ssaissf Ys claims. (ci. is-us) This invention relates to an improved fiberboard comprising vegetable ilber products of cellulose and lignin, impregnated with a resinous binder and compounded under the influence of heat and pressure. It has for its object a treatment of the vegetable material to obtain a product of maximum rigidity and strength.

Composition boards Apossessing rigidity and strength are usually prepared by impregnating paper or canvas with solutions of resinoids in a, volatile solvent. Subsequent to drying, the resin content is usually 30 to 50%. The material is then laminated to the desired thickness and subjected to heat and pressure in a hydraulic press. The ,resinoid when cured under the influencel of the heat and pressure is hard and infusible and the resulting product is of maximum rigidity and will resist ilexure and other stresses.

I have discovered that comminuted cottonseed hulls may be treated to yield products of great rigidity and strength. Broadly, this treatment consists in comminuting the hulls. impregnating them with a solution of a resinoid, driving oil the solvent, and subjecting a layer of the material to heat and pressure. g

The hulls may be satisfactorily ground in a hammer mill with nl," screen, or in an attrition or Wyllie mill. Another desirable 4method is` flaking the hulls between rotating rolls.

Comminuted cottonseed hulk have exhibited certain properties which proveA them to be well results in a product of great rigidity and mechanical strength and of improved ilnish.

With laminated phenolic sheets a pressing temperature of 150 C. has been found to be sufficient to form a finished product. The cottonseed hull compound. on the other hand, produces a much strongerfboard when pressed -at 17090. or above.

' This furnishes additional proof that the lignin is instrumental in the formation ofthe sheet. It is a matter of speculation whether the phenolic resin acts ss a plasticizer for the lignin, whether the lignin modifies the resin, whether the lignin and resin form a condensation product, or whether a co-polymerization takes place.

An apparatus by which my method may beperformed is illustrated schematically on the accompanying drawing, wherein Fig. 1 shows a comminuting and screening mill with associated drive and cottonseed y hull hopper, a steam-jacketed mixer with associated resin hopper and a receiving tray forthe comminuted material on a table below the mixer; and Fig. 2 shows a plurality of such trays positioned between platens and a movable ram for elevating the same.

'I'he following is one example of a iiberboard than 20% of phenolic resin and deficient of being a molding composition, reveal certain unique properties when pressed between two heatedv composition incorporating comminuted cotton- 'seed hulls and phenolic resin:

820 grams of cottonseed hulls. comminuted to pass a 100 mesh screen and containing 10% of hull ber are mixed with 360 grams of an aqueous phenolic resinoid syrup of 50%l solid content inr` pounds per square inch is applied. A pressing.

, time of ve minutes is sufilcient to produce a board of Y." in thickness. If a board of greater thickness isy desired the pressing time may be proportionately increased. The board hai-dens within the press and may be removed while hot.

In pl'ctiile nd for 1:83301'15 Of 80011011117 End' emciency a number of sheets are pressed simultaneously in a single press. The press may include as many as 21 vertical steam heated platens which a unique property o: cottonseed hulls. Particle size may be varied from 40 to 200 mesh. It has been determined that the comminuted hulls are composed of hull bran and hull ber, the ber content varying from to 25%. The hull bran has a very low absorbing power while the hull ber has an extremely high absorbing power. A composition consisting of hull bran alone results in a berboard of comparatively low mechanical strength. The incorporation of percentages of hull ber with the hull bran results in increased.

mechanical strength, increased resistance to exure and other stresses. The ber content may be varied from 0 to 25% and the phenolic resin content may be varied up to approximately 17%. It will thus `be seen that the properties o! iiberboard manufactured according' to this process may be varied through a wide range. Boards may be produced which are of high mechanical strength and rigidity. Conversely, a change in proportions will produce a more flexible board.

Due to the fact that no deteriorating preliminary treatment of the hulls is necessary the boards have an increased mechanical strength and resistance to exure. As the cottonseed -hulls contain oily constituents no lubrication is necessary in the press. Further, d ue to the characteristics of cottonseed hull lignin, the particles are very closely bound together with a resultant improved appearance and increase in strength.

The invention is susceptible oi numerous embodiments and adaptations The formula given in the specication is by way of illustration only and nothing in the 'specication is intended to limit the scope of the invention. Attention is directed tothe appended claims for this purpose.

What is claimed is:

1. A method of forming berboard which comprises commuting cottonseed hulls to produce hull bran of approximately 100 mesh size, adding to said bran mixing a small percentage o! phenolic lresin therewith and subjecting the resulting mass to heat and pressure until the resin is cured.

2. A method of forming fiberboard which comprises commuting cottonseed hulls to 40 to 200 mesh. adding to said comminuted hulls hull ber in the amount of approximately 10%, mixing therewith approximately 17% nf phenolic resin.' subjecting a layer of said mixture to heat and pressureuntil the product has hardened.

3. A method of forming berboard which com-r prises comminuting cottonseed hulls and huil ber to approximately mesh, the comminuted mass containing approximately 10% of hul1ber.- adding thereto a phenolic resin in an amount less than 20% oi the comminuted mass, subjecta`layer of said mixture toiheatsangvpressure until the resin is cured.

4. A method of forming berboard which coma smallpercentage ot hull ber.

prises comminuting cottonseed hulls and huir I ber to approximately 100 mesh, the commi-`l nuted mass containing from 0 to 25% of huilt Y ber, adding thereto a phenolic resin in an' amount less than 20% of the comminuted mass.; subjecting a layer or said mixture to a pressure of approximately 2000-4000 pounds per square' inch at a temperature of approximately C. until the resin is cured.

5. A method of forming berboard comprisingcomminuting cottonseed hulls and ber to ap-'j.

proximately 100 m'esh, the comnrinuted mixture' containing approximately' 20% of hull ber. add-'j ing thereto a phenolic resin in an amount less than 20%, subiectinga layer f the mixture to;

a pressure of 200G-4000 pounds per square inch at a temperature o! 170' C. until the resin-is cured and a homogeneous product formed.-

FRIIZ ROSEN THAL. 

